Any auction is "buyer beware". A pre-inspection is the best option, although not always practical. Sometimes an SS member is close by and can give a look, but still, it is not your eyes.
First: GL lists a wide variety of items. Their reps are not experts in every field. The items come in to them with little to NO information, from all over the place. Their "best guess" is what you get. Be realistic. They are not mechanics, they have no idea was something "doesn't start" - just that it "doesn't start". They are willing to provide whatever info and on-site help they can, but as with every type of auction, it is the buyer's responsibility to determine condition, and value, before bidding.
Second: One size ammo can can be "no EUC required" - another size can "require EUC". This is the government - there is little logic. I just purchased a trailer listed "H7" - it is fine. Roll of the dice. By the way, my initial EUC on the trailer went through in under a week.
Third: I drove a truck which came out of GL in Camp Shelby MS, drove to Florida, and I then drove it to SC and back to pickup the trailer. It was one of the ones which had its rebuild, and was never re-issued. Ran fine - got 6.88 MPG on the trip for the trailer, ran like a new truck. But I didn't "steal it" price wise, either. I still got more than what I paid for.
Fourth: I went to Ft Jackson for the trailer. Again, I got more than I paid for. Heck the scrap value is more than what I paid, and I didn't steal it either! Several SS members volunteered and assisted on-site, (great resource!) plus the GL reps Tim and Hector were very helpful. The trailer sat for two years, and after some "playing" we got the brakes to release and I towed it 550 miles home with NO ISSUE - but I bought in sight unseen, and I lucked out. A SS member was able to advise in advance that the tires "looked good" (and they were and all had 70# of air in them). I had no problem getting on, or around the base. I was nervous, but for me to pre-inspect was not cost effective, but I bid what I was comfortable with (allowing for the unknown), and luck was on my side.
Because my M931 had sat from rebuild May 2008 until December 2011, it ran fine, but on the way up to Ft Jackson I had time to kill so I had her completely serviced, to get a "base line". Before I left, I changed a weeping rear input shaft seal myself. At Ft Jackson, a couple of 5-tom M series cargos were present which had gone through complete rebuilds and never were issued - they looked new. I don't know if they were sold or coming up - but you can find these if you LOOK carefully at the GL auctions. Again - no guarantee, but perhaps a better "opportunity" and their prices reflect it. Stuff comes up all over the country - some is, alas, not geographically practical (just like EBAY) for the recovery, especially if one needs to deploy transport and pay for it.
My round-trip to Ft Jackson from Florida with fuel and lodging cost about $1,000. That, plus the purchase price, plus the sales tax and buyer's premium all have to be figured in - I still did very well on the trailer, and am very pleased - but I am a big boy, and it is on MY shoulders to make (and live with) the decision - best to do your research, reach out to other SS members as you have done, and "keep em' rolling".